Displacement ventilation systems and methods

ABSTRACT

A heating, ventilation, and/or air conditioning (HVAC) system includes an air handling unit configured to condition an outdoor air flow to generate a ventilation air flow. The HVAC system includes a terminal unit fluidly coupled to the air handling unit. The terminal unit includes a plenum configured to receive the ventilation air flow and a blower configured to draw a return air flow from a space serviced by the HVAC system across a heat exchanger of the terminal unit and into the plenum to condition the return air flow. The blower is configured to mix the ventilation air flow and the return air flow to generate a supply air flow. A displacement ventilation (DV) diffuser is configured to receive the supply air flow. The DV diffuser is configured to direct the supply air flow through a filter of the DV diffuser and into the space.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit of U.S.Provisional Application No. 63/218,044, entitled “AN HVAC SYSTEM,” filedJul. 2, 2021, which is herein incorporated by reference in its entiretyfor all purposes.

BACKGROUND

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present disclosure,which are described below. This discussion is believed to be helpful inproviding the reader with background information to facilitate a betterunderstanding of the various aspects of the present disclosure.Accordingly, it should be understood that these statements are to beread in this light, and not as admissions of prior art.

A heating, ventilation, and/or air conditioning (HVAC) system may beused to regulate climate parameters within an environment, such as abuilding, home, or other structure. In some cases, an air handling unitof the HVAC system may direct a flow of fresh outdoor air into abuilding to provide ventilation and improved air quality within thebuilding, while discharging a flow of return air from the building intoan ambient environment, such as the atmosphere. Particularly, the airhandling unit may include a fan assembly or other flow generating devicethat facilitates air circulation through the air handling unit and/orthroughout ductwork of the building. In certain cases, one or morediffusers may be coupled to the ductwork and configured to direct a flowof supply air received from the air handling unit into the room, zone,or other space to be conditioned by the HVAC system. The diffusers aretypically located near and/or coupled to a ceiling of the room and areconfigured to discharge the supply air generally toward a floor of theroom from the ceiling. Unfortunately, such air discharge from thediffusers may generate turbulence (e.g., air vortices) within the room,which may increase spread and/or distribution of foreign matter (e.g.,airborne particulates, contaminants) through the room.

SUMMARY

The present disclosure relates to a heating, ventilation, and/or airconditioning (HVAC) system. The HVAC system includes an air handlingunit configured to condition an outdoor air flow to generate aventilation air flow. The HVAC system also includes a terminal unitfluidly coupled to the air handling unit. The terminal unit includes aplenum configured to receive the ventilation air flow and a blowerconfigured to draw a return air flow from a space serviced by the HVACsystem across a heat exchanger of the terminal unit and into the plenumto condition the return air flow. The blower is configured to mix theventilation air flow and the return air flow to generate a supply airflow. The HVAC system includes a displacement ventilation (DV) diffuserfluidly coupled to the terminal unit and configured to receive thesupply air flow. The DV diffuser is configured to receive a filterconfigured to filter the supply air flow. The DV diffuser is configuredto direct the supply air flow through the filter and into the space.

The present disclosure also relates to a displacement ventilation (DV)diffuser. The DV diffuser includes an enclosure having an inletconfigured to receive an air flow and an outlet configured to dischargethe air flow. The enclosure is configured to receive a high efficiencyparticulate air (HEPA) filter such that the HEPA filter extends acrossthe outlet and is configured to filter the air flow. The DV diffuseralso includes a grille removeably coupled to the enclosure andconfigured to secure the HEPA filter to the enclosure.

The present disclosure also relates to a heating, ventilation, and/orair conditioning (HVAC) system. The HVAC system includes an air handlingunit having a first heat exchanger configured to dehumidify an outdoorair flow to generate a ventilation air flow. The HVAC system includes aterminal unit configured to receive the ventilation air flow. Theterminal unit includes a second heat exchanger configured to circulate aworking fluid and a blower configured to draw a return air flow acrossthe second heat exchanger to condition the return air flow and to mixthe return air flow with the ventilation air flow to generate a supplyair flow. The HVAC system also includes a displacement ventilation (DV)diffuser configured to receive the supply air flow. The DV diffuserincludes a filter configured to filter the supply air flow, where thefilter includes a high efficiency particulate air (HEPA) filter.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of this disclosure may be better understood upon readingthe following detailed description and upon reference to the drawings inwhich:

FIG. 1 is a perspective view of an embodiment of a building utilizing aheating, ventilation, and/or air conditioning (HVAC) system in acommercial setting, in accordance with an aspect of the presentdisclosure;

FIG. 2 is a schematic of an embodiment of an airside system including anair handling unit (AHU), in accordance with an aspect of the presentdisclosure;

FIG. 3 is a block diagram of an embodiment of an AHU controller, inaccordance with an aspect of the present disclosure;

FIG. 4 is a schematic of an embodiment of an HVAC system having adisplacement ventilation (DV) diffuser, in accordance with an aspect ofthe present disclosure;

FIG. 5 is a perspective view of an embodiment of a portion of an HVACsystem having a DV diffuser, in accordance with an aspect of the presentdisclosure; and

FIG. 6 is a cross-sectional view of an embodiment of a DV diffuser, inaccordance with an aspect of the present disclosure.

DETAILED DESCRIPTION

One or more specific embodiments of the present disclosure will bedescribed below. These described embodiments are only examples of thepresently disclosed techniques. Additionally, in an effort to provide aconcise description of these embodiments, all features of an actualimplementation may not be described in the specification. It should beappreciated that in the development of any such actual implementation,as in any engineering or design project, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be appreciated that such a developmenteffort might be complex and time consuming, but would nevertheless be aroutine undertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the presentdisclosure, the articles “a,” “an,” and “the” are intended to mean thatthere are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.Additionally, it should be understood that references to “oneembodiment” or “an embodiment” of the present disclosure are notintended to be interpreted as excluding the existence of additionalembodiments that also incorporate the recited features.

As briefly discussed above, a heating, ventilation, and/or airconditioning (HVAC) system may be used to regulate certain climateparameters within a space of a building, home, or other suitablestructure. For example, the HVAC system may include an air handling unithaving a fan or other flow generating device that is positioned withinan enclosure of the air handling unit. The enclosure may be in fluidcommunication with the building or other structure via an airdistribution system, such as a system of ductwork, which extends betweenthe enclosure and the building. The fan may be operable to force an airflow along an interior of the enclosure and, thus, direct air into orout of the building and/or via the air distribution system. Inparticular, the fan may enable the air handling unit to exhaust returnair from the building and/or to direct fresh outdoor air into thebuilding. Accordingly, a supply of fresh air may be circulated throughan interior of the building to improve or maintain an air quality withinthe building.

Typically, the HVAC system includes one or more diffusers that arefluidly coupled to terminal ends of the ductwork and are configured tofacilitate distribution of air from the ductwork into the rooms orspaces of the building. For example, the diffusers may be positionedadjacent to ceilings of the rooms conditioned by the HVAC system and maybe configured to discharge air from the ductwork, into the rooms orother spaces, and in directions extending generally from the ceilingstoward floors of the rooms or spaces serviced by the HVAC system.Discharge of air from the diffusers (e.g., from near the ceiling in agenerally downward direction with respect to gravity) at a relativelyhigh velocity may result in the formation of turbulence (e.g., airvortices) within the room or space. As such, the diffusers may form aportion of an overhead mixed air distribution system, for example, whichmay be configured to facilitate mixing of air within the room or spaceserviced by the HVAC system. Unfortunately, such turbulent air mixingwithin the room or space may increase spread and/or distribution offoreign matter (e.g., airborne particulates, contaminants) throughoutthe room or space. As such, conventional HVAC systems may be unsuited orill-equipped to facilitate cooling, heating, and/or ventilation ofspaces in which turbulent air mixing is undesirable, such as rooms of ahospital environment or clean room, for example.

Moreover, typical HVAC systems may mix air flows received from differentrooms, spaces, or other regions of the building during operation of theHVAC system, which may result in spread of foreign matter (e.g.,airborne contaminants) between the different rooms, spaces, and/orregions of the building. For example, a typical air handling unit of theHVAC system (e.g., an economizer of the HVAC unit) may be configured toreceive a first flow of return air from a first room or zone serviced bythe HVAC system and to receive a second flow of return air from a secondroom or zone serviced by the HVAC system. The air handling unit may mixat least a portion of the first and second air flows with one anotherand with outdoor air received from an ambient environment (e.g., theatmosphere) to form a supply air flow. The air handling unit maysubsequently direct portions of the supply air flow back to the firstand second rooms or zones. As a result, conventional HVAC systems mayfacilitate undesirable spread of foreign matter from the first room tothe second room, and vice versa.

It is now recognized that it is desirable to facilitate conditioning(e.g., cooling, heating, ventilation, filtration) of spaces serviced byan HVAC system while also mitigating or substantially eliminating mixing(e.g., turbulent mixing) of air within each of the spaces, and whilemitigating or substantially eliminating exchange of air between thespaces. Accordingly, embodiments of the present disclosure are directedtoward an improved HVAC system that is configured to facilitate andenable displacement ventilation in the spaces serviced by the HVACsystem to substantially reduce mixing (e.g., turbulent mixing) of airwithin the space, as compared to typical HVAC systems having overheadmixed air distribution systems. Moreover, the improved HVAC systemdisclosed herein is configured to mitigate or substantially eliminateexchange of air between individual rooms, zones, or other spacesserviced by the HVAC system to substantially inhibit transmission offoreign matter (e.g., airborne contaminants) between the individualspaces. These and other features will be described below with referenceto the drawings.

Turning now to the drawings, FIG. 1 is a perspective view of anembodiment of a building 10 that may be serviced by a heating,ventilation, and/or air conditioning (HVAC) system 100. The HVAC system100 may include a plurality of HVAC devices (e.g., heaters, chillers,air handling units, pumps, fans, thermal energy storage units, etc.)configured to provide heating, cooling, air conditioning, ventilation,and/or other services for the building 10. For example, in theillustrated embodiment, the HVAC system 100 is shown to include awaterside system 120 and an airside system 130. The waterside system 120may provide a heated fluid and/or a chilled fluid to an air handlingunit of the airside system 130. The airside system 130 may use theheated fluid and/or the chilled fluid to heat or cool an airflowprovided to the building 10.

In the illustrated embodiment, the HVAC system 100 includes a chiller102, a boiler 104, and an air handling unit (AHU) 106 (e.g., a rooftopunit). The waterside system 120 may use the boiler 104 and the chiller102 to heat or cool a working fluid (e.g., water, glycol, etc.) and maycirculate the working fluid to the AHU 106. In various embodiments, theHVAC devices of the waterside system 120 may be located in or around thebuilding 10 or at an offsite location such as a central plant (e.g., achiller plant, a steam plant, a heat plant, etc.) that serves one ormore portions of the building 10. The working fluid may be heated in theboiler 104 or cooled in the chiller 102, depending on whether heating orcooling is desired in the building 10. The boiler 104 may add heat tothe circulated fluid, for example, by burning a combustible material(e.g., natural gas) or using an electric heating element. The chiller102 may place the circulated fluid in a heat exchange relationship withanother fluid (e.g., a refrigerant) in a heat exchanger (e.g., anevaporator) to absorb heat from the circulated fluid. The working fluidfrom the chiller 102 and/or the boiler 104 may be transported to the AHU106 via piping 108.

The AHU 106 may place the working fluid in a heat exchange relationshipwith an air flow passing through the AHU 106 (e.g., via one or morestages of cooling coils and/or heating coils). The air flow may be, forexample, outside air, return air from within the building 10, or acombination of both. The AHU 106 may transfer heat between the air flowand the working fluid to provide heating or cooling for the air flow.For example, the AHU 106 can include one or more fans or blowersconfigured to pass the air flow over or through a heat exchangercontaining the working fluid. The working fluid may then return to thechiller 102 and/or the boiler 104 via piping 110.

The airside system 130 may deliver the air flow supplied by the AHU 106(i.e., the supply air flow) to the building 10 via air supply ducts 112and may provide return air from the building 10 to the AHU 106 via airreturn ducts 114. In some embodiments, the airside system 130 includesmultiple variable air volume (VAV) units 116. For example, in theillustrated embodiment, the airside system 130 is shown to include aseparate VAV unit 116 on each floor or zone of building 10. The VAVunits 116 may include dampers or other flow control elements that can beoperated to control an amount of the supply air flow provided toindividual zones of the building 10. In other embodiments, the airsidesystem 130 delivers the supply air flow into one or more zones of thebuilding 10 (e.g., via the supply ducts 112) without using theintermediate VAV units 116 or other flow control elements. The AHU 106can include various sensors (e.g., temperature sensors, pressuresensors, etc.) configured to measure attributes of the supply air flow.The AHU 106 may receive input from sensors located within the AHU 106and/or within the building zone and may adjust the flow rate,temperature, or other attributes of the supply air flow through the AHU106 to achieve setpoint conditions for the building zone.

FIG. 2 is a schematic of an embodiment of an airside system 200, such asthe airside system 130. The airside system 200 may include a subset ofthe HVAC devices that may be included in the HVAC system 100 (e.g., theAHU 106, the VAV units 116, the ducts 112, 114, fans, dampers, etc.) andmay be located in or around the building 10. The airside system 200 mayoperate to heat or cool an air flow provided to the building 10 using aheated or chilled fluid provided by the waterside system 120.

In the illustrated embodiment of FIG. 2 , the airside system 200 isshown to include an economizer-type air handling unit (AHU) 202. Theeconomizer-type AHU 202 may vary the amount of outside air and returnair used by the air handling unit for heating or cooling. For example,the AHU 202 may receive return air 204 from building zone 206 via returnair duct 208 and may deliver supply air 210 to the building zone 206 viasupply air duct 212. In some embodiments, the AHU 202 (e.g., the AHU106) is a rooftop unit located on the roof of the building 10 orotherwise positioned to receive both return air 204 and outside air 214.The AHU 202 may be configured to operate exhaust air damper 216, mixingdamper 218, and outside air damper 220 to control an amount of theoutside air 214 and the return air 204 is combined to form supply air210. Any return air 204 that does not pass through mixing damper 218 maybe exhausted from the AHU 202 through exhaust damper 216 as exhaust air222.

Each of dampers 216, 218, 220 may be operated by an actuator. Forexample, the exhaust air damper 216 may be operated by actuator 224,mixing damper 218 may be operated by actuator 226, and outside airdamper 220 may be operated by actuator 228. Actuators 224, 226, 228 maycommunicate with an AHU controller 230 via a communications link 232.The actuators 224, 226, 228 may receive control signals from the AHUcontroller 230 and may provide feedback signals to the AHU controller230. Feedback signals can include, for example, an indication of acurrent actuator or damper position, an amount of torque or forceexerted by the actuator, diagnostic information (e.g., results ofdiagnostic tests performed by actuators 224, 226, 228), statusinformation, commissioning information, configuration settings,calibration data, and/or other types of information or data that can becollected, stored, or used by the actuators 224, 226, 228. The AHUcontroller 230 may be an economizer controller configured to use one ormore control algorithms (e.g., state-based algorithms, extremum seekingcontrol (ESC) algorithms, proportional-integral (PI) control algorithms,proportional-integral-derivative (PID) control algorithms, modelpredictive control (MPC) algorithms, feedback control algorithms, etc.)to control actuators 224, 226, 228.

In the illustrated embodiment of FIG. 2 , the AHU 202 is shown toinclude a cooling coil 234, a heating coil 236, and a fan 238 positionedwithin supply air duct 212. The fan 238 may be configured to forcesupply air 210 across the cooling coil 234 and/or the heating coil 236and provide the supply air 210 to the building zone 206. The AHUcontroller 230 may communicate with the fan 238 via communications link240 to control a flow rate of the supply air 210. In some embodiments,the AHU controller 230 controls an amount of heating or cooling appliedto the supply air 210 by modulating a speed of the fan 238.

The cooling coil 234 may receive a chilled fluid from the watersidesystem 120 (via piping 242) and may return the chilled fluid towaterside system 120 via piping 244. A valve 246 may be positioned alongthe piping 242 or the piping 244 to control a flow rate of the chilledfluid through cooling coil 234. In some embodiments, the cooling coil234 includes multiple stages of cooling coils that may be independentlyactivated and deactivated (e.g., by the AHU controller 230, bysupervisory controller 266, etc.) to modulate an amount of coolingapplied to the supply air 210.

The heating coil 236 may receive a heated fluid from the watersidesystem 120 via piping 248 and may return the heated fluid to thewaterside system 120 via piping 250. A valve 252 may be positioned alongthe piping 248 and/or the piping 250 to control a flow rate of theheated fluid through the heating coil 236. In some embodiments, theheating coil 236 includes multiple stages of heating coils that may beindependently activated and deactivated (e.g., by the AHU controller230, by the supervisory controller 266, etc.) to modulate an amount ofheating applied to the supply air 210.

Each of the valves 246 and 252 may be controlled by an actuator. Forexample, valve 246 may be controlled by an actuator 254, and the valve252 may be controlled by an actuator 256. The actuators 254, 256 maycommunicate with the AHU controller 230 via communications links 258,260. The actuators 254, 256 may receive control signals from the AHUcontroller 230 and may provide feedback signals to the AHU controller230. In some embodiments, the AHU controller 230 receives a measurementof the supply air temperature from a temperature sensor 262 positionedin the supply air duct 212 (e.g., downstream of the cooling coil 234and/or the heating coil 236). The AHU controller 230 may also receive ameasurement of the temperature of the building zone 206 from atemperature sensor 264 located in the building zone 206.

In some embodiments, the AHU controller 230 operates the valves 246 and252 via the actuators 254, 256 to modulate an amount of heating orcooling provided to the supply air 210 (e.g., to achieve a setpointtemperature for the supply air 210 or to maintain the temperature of thesupply air 210 within a setpoint temperature range). The positions ofthe valves 246 and 252 affect the amount of heating or cooling providedto the supply air 210 by the cooling coil 234 or the heating coil 236and may correlate with the amount of energy consumed to achieve adesired supply air temperature. The AHU controller 230 may control thetemperature of the supply air 210 and/or the building zone 206 byactivating or deactivating the coils 234, 236, adjusting a speed of thefan 238, or a combination of both.

In the illustrated embodiment of FIG. 2 , the airside system 200 isshown to include a supervisory controller 266 and a client device 268.The supervisory controller 266 may include one or more computer systems(e.g., servers, supervisory controllers, subsystem controllers, etc.)that serve as system level controllers, application or data servers,head nodes, or master controllers for the airside system 200, thewaterside system 120, the HVAC system 100, and/or other controllablesystems that serve the building 10. The supervisory controller 266 maycommunicate with multiple downstream building systems or subsystems(e.g., the HVAC system 100, a security system, a lighting system,waterside system 120, etc.) via a communications link 270 according tolike or disparate protocols (e.g., LON, BACnet, etc.). In variousembodiments, the AHU controller 230 and the supervisory controller 266may be separate or integrated. In an integrated implementation, the AHUcontroller 230 may be a software module configured for execution by aprocessor of the supervisory controller 266.

In some embodiments, the AHU controller 230 receives information fromthe supervisory controller 266 (e.g., commands, set points, operatingboundaries, etc.) and provides information to the supervisory controller266 (e.g., temperature measurements, valve or actuator positions,operating statuses, diagnostics, etc.). For example, the AHU controller230 may provide the supervisory controller 266 with temperaturemeasurements from the temperature sensors 262, 264, equipment on/offstates, equipment operating capacities, and/or any other informationthat may be used by the supervisory controller 266 to monitor or controla variable state or condition within the building zone 206.

The client device 268 may include one or more human-machine interfacesor client interfaces (e.g., graphical user interfaces, reportinginterfaces, text-based computer interfaces, client-facing web services,web servers that provide pages to web clients, etc.) for controlling,viewing, or otherwise interacting with the HVAC system 100, itssubsystems, and/or devices. The client device 268 may be a computerworkstation, a client terminal, a remote or local interface, or anyother type of user interface device. The client device 268 may be astationary terminal or a mobile device. For example, the client device268 may be a desktop computer, a computer server with a user interface,a laptop computer, a tablet, a smartphone, a PDA, or any other type ofmobile or non-mobile device. The client device 268 may communicate withsupervisory the controller 266 and/or the AHU controller 230 via acommunications link 272.

FIG. 3 is a schematic of an embodiment of the AHU controller 230. TheAHU controller 230 may be configured to monitor and control variouscomponents of the AHU 202 using any of a variety of control techniques(e.g., state-based control, on/off control, proportional control,proportional-integral (PI) control, proportional-integral-derivative(PID) control, extremum seeking control (ESC), model predictive control(MPC), etc.). The AHU controller 230 may receive set points from thesupervisory controller 266 and measurements from sensors 318 and mayprovide control signals to actuators 320 and the fan 238.

The sensors 318 may include any of the sensors shown in FIG. 2 and/orany other sensor configured to monitor any of a variety of variablesused by the AHU controller 230. Variables monitored by the sensors 318may include, for example, zone air temperature, zone air humidity, zoneoccupancy, zone carbon dioxide (CO2) levels, zone particulate matter(PM) levels, outdoor air temperature, outdoor air humidity, outdoor airCO2 levels, outdoor air PM levels, damper positions, valve positions,fan status, supply air temperature, supply air flow rate, or any othervariable of interest to the AHU controller 230.

The actuators 320 may include any of the actuators shown in FIG. 2and/or any other actuator controllable by the AHU controller 230. Forexample, the actuators 320 may include the actuator 224 configured tooperate the exhaust air damper 216, the actuator 226 configured tooperate the mixing damper 218, the actuator 228 configured to operatethe outside air damper 220, the actuator 254 configured to operate thevalve 246, and/or the actuator 256 configured to operate the valve 252.The actuators 320 may receive control signals from the AHU controller230 and may provide feedback signals to the AHU controller 230.

The AHU controller 230 may control the AHU 202 by controllably changingand outputting a control signals provided to the actuators 320 and thefan 238. In some embodiments, the control signals include commands forthe actuators 320 to set the dampers 216, 218, 220 and/or the valves 246and 252 to specific positions to achieve a target value for a variableof interest (e.g., supply air temperature, supply air humidity, flowrate, etc.). In some embodiments, the control signals include commandsfor the fan 238 to operate at a specific operating speed and/or toachieve a specific air flow rate. The control signals may be provided tothe actuators 320 and the fan 238 via a communications interface 302.The AHU 202 may use the control signals an input to adjust the positionsof the dampers 216, 218, 220 control the relative proportions of theoutside air 214 and the return air 204 provided to the building zone206.

The AHU controller 230 may receive various inputs via the communicationsinterface 302. Inputs received by the AHU controller 230 may include setpoints from the supervisory controller 266, measurements from thesensors 318, a measured or observed position of the dampers 216, 218,220 or valves 246 and 252, a measured or calculated amount of powerconsumption, an observed fan speed, temperature, humidity, air quality,or any other variable that may be measured or calculated in or aroundthe building 10.

The AHU controller 230 includes logic that adjusts the control signalsto achieve a target outcome. In some operating modes, the control logicimplemented by the AHU controller 230 utilizes feedback of an outputvariable. The logic implemented by the AHU controller 230 may also oralternatively vary a manipulated variable based on a received inputsignal (e.g., a set point). Such a set point may be received from a usercontrol (e.g., a thermostat), a supervisory controller (e.g., thesupervisory controller 266), or another upstream device via acommunications network (e.g., a BACnet network, a LonWorks network, aLAN, a WAN, the Internet, a cellular network, etc.).

In the illustrated embodiment of FIG. 3 , the AHU controller 230 isshown to include the communications interface 302. The communicationsinterface 302 may be or include wired or wireless communicationsinterfaces (e.g., jacks, antennas, transmitters, receivers,transceivers, wire terminals, etc.) for conducting data communicationswith various components of the AHU 202 or other external systems ordevices. In various embodiments, communications via the communicationsinterface 302 may be direct (e.g., local wired or wirelesscommunications) or via a communications network (e.g., a WAN, theInternet, a cellular network, etc.). For example, the communicationsinterface 302 can include an Ethernet card and port for sending andreceiving data via an Ethernet-based communications link or network. Inanother example, the communications interface 302 may include a Wi-Fitransceiver for communicating via a wireless communications network. Inanother example, the communications interface 302 may include a cellularor mobile phone transceiver, a power line communications interface, anEthernet interface, or any other type of communications interface.

The AHU controller 230 may include a processing circuit 304 having aprocessor 306 and a memory 308. The processor 306 may be a generalpurpose or specific purpose processor, an application specificintegrated circuit (ASIC), one or more field programmable gate arrays(FPGAs), a group of processing components, or other suitable processingcomponents. The processor 306 is configured to execute computer code orinstructions stored in the memory 308 or received from other computerreadable media (e.g., CDROM, network storage, a remote server, etc.).

The memory 308 may include one or more devices (e.g., memory units,memory devices, storage devices, etc.) for storing data and/or computercode for completing and/or facilitating the various processes describedin the present disclosure. The memory 308 may include random accessmemory (RAM), read-only memory (ROM), hard drive storage, temporarystorage, non-volatile memory, flash memory, optical memory, or any othersuitable memory for storing software objects and/or computerinstructions. The memory 308 may include database components, objectcode components, script components, or any other type of informationstructure for supporting the various activities and informationstructures described in the present disclosure. The memory 308 may becommunicably connected to the processor 306 via the processing circuit304 and may include computer code for executing (e.g., by the processor306) one or more processes described herein.

The memory 308 may include any of a variety of functional components(e.g., stored instructions or programs) that provide the AHU controller230 with the ability to monitor and control the AHU 202. For example,the memory 308 is shown to include a data collector 310 which operatesto collect the data received via the communications interface 302 (e.g.,set points, measurements, feedback from the actuators 320 and the fan238, etc.). The data collector 310 may provide the collected data to anactuator controller 312 and a fan controller 314, which use thecollected data to generate control signals for the actuators 320 and thefan 238, respectively. The particular type of control methodology usedby the actuator controller 312 and the fan controller 314 (e.g.,state-based control, PI control, PID control, ESC, MPC, etc.) may varydepending on the configuration of the AHU controller 230 and may beadapted for various implementations.

It should be appreciated that any of the features described herein maybe incorporated with the HVAC system 100 or other HVAC systems.Additionally, while the features disclosed herein are described in thecontext of embodiments that directly heat and cool a supply air streamprovided to a building or other load, embodiments of the presentdisclosure may be applicable to other HVAC systems as well. For example,the features described herein may be applied to mechanical coolingsystems, free cooling systems, chiller systems, or other heat pump orrefrigeration applications.

As briefly discussed above, embodiments of the present disclosure aredirected to an improved HVAC system configured to facilitateconditioning (e.g., cooling, heating, ventilation, filtration) of spaces(e.g., rooms or zones of the building 10) serviced by the HVAC systemwhile also mitigating or substantially eliminating mixing (e.g.,turbulent mixing) of air within each of the spaces, and while mitigatingor substantially eliminating exchange of air between the individualspaces. To provide context for the following discussion, FIG. 4 is aschematic of an embodiment of an HVAC system 400 configured to providethe aforementioned advantageous features. For clarity, it should beunderstood that the HVAC system 400 may include a portion of and/or allof the components of the HVAC system 100.

The HVAC system 400 includes an air handling unit 402 (e.g., the AHU106, a dedicated outdoor air system [DOAS]) that may be fluidly coupledto a terminal unit 404 via first ductwork 406 (e.g., one or moreconduits, a ventilation duct). The air handling unit 402 is configuredto provide a flow of ventilation air 408 to the terminal unit 404 viathe first ductwork 406. For example, the air handling unit 402 mayinclude a first enclosure 410 configured to house or more climatemanagement components of the air handling unit 402, such as a filter412, a first heat exchanger 414 (e.g., an evaporator, a hydronic heatexchanger), a first blower 420, and/or other suitable climate managementcomponents of the air handling unit 402 (e.g., a heating coil, anelectric furnace, a gas furnace). The first blower 420 may be operableto draw a flow of outdoor air 422 (e.g., from the atmosphere 424, froman outdoor environment) into the first enclosure 410 (e.g., via an inlet426 of the first enclosure 410) and to direct the outdoor air 422 acrossone or more climate management components of the air handling unit 402.For example, the first blower 420 may direct the outdoor air 422 acrossthe filter 412 and the first heat exchanger 414. As discussed in detailbelow, the first heat exchanger 414 may be configured to absorb thermalenergy from the outdoor air 422 to enable generation of the ventilationair 408, which may have a temperature that is less than a temperature ofthe outdoor air 422. Moreover, the first heat exchanger 414 may causecondensation of moisture that may be suspended in the outdoor air 422 ona surface of the first heat exchanger 414. To this end, the first heatexchanger 414 may also facilitate dehumidification of the outdoor air422, such that a relative humidity value of the ventilation air 408discharged from the first heat exchanger 414 is less than a relativehumidity value of the outdoor air 422 entering the air handling unit402.

The terminal unit 404 includes a second enclosure 430 that may befluidly coupled to the first enclosure 410 of the air handling unit 402via the first ductwork 406. The first blower 420 may be operable todirect the ventilation air 408 through the first ductwork 406 and intothe second enclosure 430 (e.g., into a plenum defined by the secondenclosure 430). In some embodiments, the terminal unit 404 includes asecond blower 432 configured to draw the ventilation air 408 from theair handling unit 402 into the second enclosure 430.

The terminal unit 404 may include a second heat exchanger 434. Forexample, the second heat exchanger 434 may be coupled to the secondenclosure 430 and be disposed external to the second enclosure 430. Inother embodiments, the second heat exchanger 434 may be disposed withinan interior of the second enclosure 430 and/or be otherwise fluidlycoupled to the interior of the second enclosure 430. The second blower432 may be configured to draw a flow of return air 440 from a space(e.g., a room 442 or zone) to be conditioned by the HVAC system 400 anddirect the return air 440 across the second heat exchanger 434 and intothe second enclosure 430. As discussed below, the second heat exchanger434 may be configured to facilitate cooling and/or heating of the returnair 440 directed thereacross, such that the second heat exchanger 434may output a flow of conditioned return air 444.

In some embodiments, the second heat exchanger 434 may be fluidlycoupled to a chiller system 446 (e.g., HVAC system, heat pump) oranother thermal management component via a supply line 448 (e.g., achilled water supply line) and a return line 449 (e.g., a chilled waterreturn line). The chiller system 446 may be configured to circulate achilled working fluid (e.g., water, brine) through the second heatexchanger 434, such that the chilled working fluid may absorb thermalenergy from the return air 440 that may be directed across the secondheat exchanger 434 via the second blower 432. As discussed below, thesecond heat exchanger 434 may operate as a sensible cooling coil (e.g.,at a temperature above a dew point temperature of the return air 440) toreduce a temperature of the return air 440 without substantiallyadjusting a humidity of the return air 440. As such, the second heatexchanger 434 may inhibit or substantially limit formation ofcondensation and/or accumulation of condensation on a surface of thesecond heat exchanger 434.

It should be appreciated that, in certain embodiments, the second heatexchanger 434 may be configured to circulate a heated working fluid, inlieu of a chilled working fluid, to facilitate heating of the return air440 that may be directed across the second heat exchanger 434. Moreover,in some embodiments, operation of the second heat exchanger 434 may betemporarily suspended, such that the return air 440 may be directedacross the second heat exchanger 434 without substantially cooling orheating of the return air 440. It should be understood that, as usedherein, any air flow discharged from the second heat exchanger 434 maybe referred to as the “conditioned return air 444.” That is, theconditioned return air 444 may be indicative of return air 440 that hasbeen cooled by the second heat exchanger 434, return air 440 that hasbeen heated by the second heat exchanger 434, and/or return air 440 thathas been directed across the second heat exchanger 434 without beingsubstantially cooled or heated by the second heat exchanger 434.

The terminal unit 404 may be configured to facilitate mixing of theventilation air 408 received from the air handling unit 402 and theconditioned return air 444 discharged from the second heat exchanger434. For example, the terminal unit 404 may include one or more baffles,passages, fans, dampers, or other components that may enhance orotherwise facilitate mixing of the ventilation air 408 and theconditioned return air 444. In any case, via mixing of the ventilationair 408 and the conditioned return air 444, the terminal unit 404 maygenerate of a flow of supply air 450 that may include at least a portionof the ventilation air 408 and at least a portion of the conditionedreturn air 444. The terminal unit 404 may be fluidly coupled to a thirdenclosure 452 (e.g., a housing) of a displacement ventilation (DV)diffuser 454 via second ductwork 456. As discussed below, the DVdiffuser 454 may be positioned near or adjacent to a floor of the room442 and be configured to discharge the supply air 450 into the room 442and along the floor. To this end, the second blower 432 may beconfigured to direct the supply air 450 through the second ductwork 456,through the third enclosure 452 of the DV diffuser 454, and into theroom 442 via an outlet 458 of the DV diffuser 454.

The DV diffuser 454 may be configured to accommodate (e.g., receive,support, contain) a filter 459 that extends across the outlet 458 of theDV diffuser 454. The filter 459 may be sealed to a perimeter of theoutlet 458 via a gasket, bracket, harness, or other suitable seal. Insome embodiments, the filter 412 may be a high efficiency particulateair (HEPA) filter configured to capture or trap, for example, 90 percentof particulate matter (e.g., foreign matter, airborne contaminants)suspended in an air flow (e.g., the supply air 450) directed across thefilter 459, such as particulate matter having particles with a sizebetween 1.0 microns and 3.0 microns in diameter.

In some embodiments, the terminal unit 404 may include a reheat coil 460(e.g., a third heat exchanger) that may be operable in addition to, orin lieu of, the second heat exchanger 434 to increase a temperature ofthe supply air 450 prior to delivery of the supply air 450 to the DVdiffuser 454. For example, the reheat coil 460 may be configured toreceive a flow of heated working fluid (e.g., heated water) and enablethe heated working fluid to reject heat (e.g., thermal energy) to themixture of ventilation air 408 and conditioned return air 444 that maybe directed across the reheat coil 460 via the second blower 432. Assuch, it should be understood that any one or combination of the firstheat exchanger 414, the second heat exchanger 434, and the reheat coil460 may be included in the HVAC system 400 and may be operable tofacilitate adjustment in a temperature value and/or a humidity level ofthe supply air 450. Moreover, it should be appreciated that relativelocations of any of the first and/or second heat exchangers 414, 434,the first and/or second blowers 420, 432, the reheat coil 460, and/orother components of the HVAC system 400 are not limited to the locationsshown in the illustrated embodiment of FIG. 4 . As a non-limitingexample, the second heat exchanger 434 may be located within the secondenclosure 430, external to the second enclosure 430, adjacent to reheatcoil 460, or at another suitable location. Similarly, the reheat coil460 may be located within the second enclosure 430 or external to thesecond enclosure 430.

In some embodiments, the terminal unit 404 may include an additionalfilter 470 (e.g., a HEPA filter, a MERV-6 filter, a MERV-8 filter)configured to filter the return air 440 entering the terminal unit 404.For example, the additional filter 470 may be positioned adjacent to thesecond heat exchanger 434 and be configured to filter the return air 440prior to the return air 440 being directed across the second heatexchanger 434. The terminal unit 404 may include an access panel toenable removal and/or replacement of the additional filter 470 via anoccupant located within the room 442.

In some embodiments, the HVAC system 400 includes one or more sensors480 configured to acquire feedback or other data indicative of one ormore operational parameters of the HVAC system 400. For example, the oneor more sensors 480 may include a first sensor 482 configured to acquiredata or feedback indicative of a temperature and/or a humidity of theoutdoor air 422, a second sensor 484 configured to acquire data orfeedback indicative of a temperature and/or a humidity of theventilation air 408, a third sensor 486 configured to acquire data orfeedback indicative of a temperature and/or a humidity of the return air440, a fourth sensor 488 configured to acquire data or feedbackindicative of a temperature and/or a humidity of the conditioned returnair 444, a fifth sensor 490 configured to acquire data or feedbackindicative of a temperature and/or a humidity of the supply air 450, asixth sensor 492 (e.g., a thermostat) configured to measure an ambienttemperature and/or a humidity within the room 442, a seventh sensor 494configured to measure a temperature of a working fluid 496 supplied tothe second heat exchanger 434 (e.g., via the supply line 448), and/orother suitable sensor(s).

The HVAC system 400 may include a controller 500 (e.g., the AHUcontroller 230, a control system, a thermostat, a control panel, controlcircuitry) that is communicatively coupled to one or more components ofthe HVAC system 400 and is configured to monitor, adjust, and/orotherwise control operation of one or more components of the HVAC system400. For example, one or more control transfer devices, such as wires,cables, wireless communication devices, and the like, maycommunicatively couple the first and/or second blowers 420, 432, thechiller system 446, the sensors 480, one or more dampers, one or morevalves, and/or any other suitable components of the HVAC system 400 tothe controller 500. The first and/or second blowers 420, 432, thechiller system 446, and/or the sensors 480 may each have one or morecommunication components that facilitate wired or wireless (e.g., via anetwork) communication with the controller 500. In some embodiments, thecommunication components may include a network interface that enablesthe components of the HVAC system 400 to communicate via variousprotocols such as EtherNet/IP, ControlNet, DeviceNet, or any othercommunication network protocol. Alternatively, the communicationcomponents may enable the components of the HVAC system 400 tocommunicate via mobile telecommunications technology, Bluetooth®,near-field communications technology, and the like. As such, the firstand/or second blowers 420, 432, the chiller system 446, and/or thesensors 480 may wirelessly communicate data and/or control signalsbetween each other.

In some embodiments, the controller 500 may be a component of or mayinclude the AHU controller 230. In other embodiments, the controller 500may be a standalone controller, a dedicated controller, or anothersuitable controller included in the HVAC system 400. In any case, thecontroller 500 is configured to control components of the HVAC system400 in accordance with the techniques discussed herein. The controller500 includes processing circuitry 502, such as a microprocessor, whichmay execute software (e.g., executable instructions, code) forcontrolling components of the HVAC system 400. The processing circuitry502 may include multiple microprocessors, one or more “general-purpose”microprocessors, one or more special-purpose microprocessors, and/or oneor more application specific integrated circuits (ASICS), or somecombination thereof. For example, the processing circuitry 502 mayinclude one or more reduced instruction set (RISC) processors.

The controller 500 may also include a memory device 504 (e.g., a memory)that may store information, such as instructions, control software, lookup tables, configuration data, code, etc. The memory device 504 mayinclude a volatile memory, such as random access memory (RAM), and/or anonvolatile memory, such as read-only memory (ROM). The memory device504 may store a variety of information and may be used for variouspurposes. For example, the memory device 504 may storeprocessor-executable instructions including firmware or software for theprocessing circuitry 502 execute, such as instructions for controllingcomponents of the HVAC system 400. In some embodiments, the memorydevice 504 is a tangible, non-transitory, machine-readable-medium thatmay store machine-readable instructions for the processing circuitry 502to execute. The memory device 504 may include ROM, flash memory, a harddrive, or any other suitable optical, magnetic, or solid-state storagemedium, or a combination thereof. The memory device 504 may store data,instructions, and any other suitable data. As discussed in detail below,the controller 500 may be configured to control operation of the HVACsystem 400 to facilitate conditioning (e.g., cooling, heating,ventilation, filtration) of the room 442 while mitigating orsubstantially eliminating mixing (e.g., turbulent mixing) of air withinthe room 442 and while mitigating or substantially eliminating exchangeof air between the room 442 and other rooms that may be serviced by theHVAC system 400 (e.g., other rooms in the building 10).

To facilitate the following discussion, FIG. 5 is a perspective view ofan embodiment of a portion of the HVAC system 400. In the illustratedembodiment, the HVAC system 400 includes an exhaust duct 510 (e.g.,grille) configured to receive and direct exhaust air 512 from the room442. For example, an exhaust fan 514 or blower may be configured to drawthe exhaust air 512 through the exhaust duct 510 and discharge theexhaust air 512 to the atmosphere. It should be noted that the exhaustfan 514 may not recirculate the exhaust air 512 to another room, zone,or space within the building 10. In this manner, the HVAC system 400 mayblock or substantially inhibit transfer of the exhaust air 512, whichmay contain airborne contaminants, from the room 442 to another room ofthe building 10, for example, or vice versa. In other words, the airhandling unit 402 and the terminal unit 404 may not receive the exhaustair 512 from the exhaust duct 510.

As shown in the illustrated embodiment of FIG. 5 , the DV diffuser 454may be located adjacent to a floor 520 of the room 442. In someembodiments, a cross-sectional area of the outlet 458 and across-sectional area of the filter 459 may be relatively large. As aresult, the outlet 458 and the filter 459 may enable supply of thesupply air 450 to the room 442 at a relatively low velocity. In thisway, the DV diffuser 454 may direct the supply air 450 along the floor520 in a manner that mitigates air turbulence in the room 442, asdiscussed in further detail below.

The following discussion continues with concurrent reference to FIGS. 4and 5 . As discussed above, the HVAC system 400 is configured tofacilitate conditioning of the room 442 while mitigating orsubstantially eliminating mixing (e.g., turbulent mixing) of air withinthe room 442 and while mitigating or substantially eliminating exchangeof air between the room 442 and other rooms serviced by the HVAC system400 (e.g., other rooms in the building 10). The controller 500 may beconfigured to operate the HVAC system 400 to provide a desired amount ofventilation (e.g., air exchange) within the room 442 while alsoproviding conditioning (e.g., cooling) to the room 442.

For example, to provide ventilation within the room 442, the controller500 may operate the first blower 420 to draw outdoor air 422 into thefirst enclosure 410 of the air handling unit 402. In some embodiments,the controller 500 may receive feedback from the first sensor 482indicative of temperature of the outdoor air 422 and/or of a humidity ofthe outdoor air 422. In response to a determination that a humiditylevel of the outdoor air 422 is above a target humidity level associatedwith the room 442, the controller 500 may instruct the air handling unit402 to operate in a dehumidification mode to dehumidify the outdoor air422. In particular, the controller 500 may operate components of the airhandling unit 402 to circulate working fluid through the first heatexchanger 414 at a temperature that is below a dew point temperature ofthe outdoor air 422. As a result, water vapor (e.g., moisture) suspendedin the outdoor air 422 may condense and be removed from the outdoor air422, such that the ventilation air 408 output by the air handling unit402 has a humidity level that is less than a humidity level of theoutdoor air 422 entering the air handling unit 402. In some embodiments,the controller 500 may receive feedback indicative of the humidity levelof the ventilation air 408 from the second sensor 484. The controller500 may be configured to utilize feedback from the first sensor 482, thesecond sensor 484, or both, to operate components of the air handlingunit 402 to achieve a humidity level of the ventilation air 408 that issubstantially similar to or below (e.g., within a threshold range of,within a threshold percentage of) the target humidity level for the room442.

As discussed below, the terminal unit 404 may be configured tofacilitate conditioning (e.g., cooling) of the room 442 in addition toany cooling capacity that may be provided via the first heat exchanger414 of the air handling unit 402. Accordingly, the air handling unit 402may not be operated to satisfy an entire cooling demand of the room 442.Thus, an overall size of the air handling unit 402 may be reduced, ascompared to typical air handling units. That is, the air handling unit402 may primarily operate to dehumidify the flow of outdoor air 422,instead of operating to provide an amount of conditioned air that issuitable to satisfy the cooling demand of the room 442. In this way, asize of the first ductwork 406 configured to deliver the ventilation air408 may also be reduced as compared to conventional systems.

In some embodiments, the air handling unit 402 may not receive a flow ofthe exhaust air 512 from the exhaust duct 510. That is, the air handlingunit 402 may not include an energy recovery wheel or similar heatexchange device for transferring thermal energy between the exhaust air512 and the outdoor air 422 and/or between the exhaust air 512 and theventilation air 408. As a result, the HVAC system 400 may substantiallyreduce introduction of foreign matter (e.g., airborne contaminants) thatmay be included in the exhaust air 512 into the outdoor air 422 and/orthe ventilation air 408. Further, via elimination of an energy recoverywheel or similar device in the air handling unit 402, an overall size ofthe air handling unit 402 may be further reduced (e.g., as compared toconventional air handling units having an energy recovery wheel).However, it should be appreciated that, in certain embodiments, the airhandling unit 402 may indeed include an energy recovery wheel or similarheat exchange device. That is, the air handling unit 402 may receive atleast a portion of an exhaust air flow from the building 10 and utilizethe energy recovery wheel or similar device to pre-cool or pre-heat theoutdoor air 422 entering the air handling unit 402, for example.

The controller 500 may operate the second blower 432 to draw the returnair 440 across the additional filter 470, mix the filtered return air(e.g., the conditioned return air 444) with the ventilation air 408 toform the supply air 450, and direct the supply air 450 toward the DVdiffuser 454. In some embodiments, the second blower 432 and theadditional filter 470 may cooperate to reduce an amount of air changesthat the air handling unit 402 may need to provide to achieve aparticular air exchange in the room 442. As a non-limiting example, in ahospital or health care environment, it may be desirable to achieve fourair changes per hour in the room 442. For clarity, as used herein, an“air change” of the room 442 or other space may refer to a complete orsubstantial replacement of air within the room 442 or other space withreplenished air (e.g., fresh air, filtered air) supplied via the DVdiffuser 454. Indeed, the replenished air may include outdoor air 442and air from the room 422 that is re-filtered (e.g., via the terminalunit 402). For example, the air handling unit 402 may be operable toprovide a volume of air to enable two air changes of the room 442 viathe outdoor air 422 drawn into the HVAC system 400. The terminal unit404 may be operable to provide an additional volume of air to enable theremaining two air exchanges of the room 442 via the return air 440 thatis filtered via the additional filter 470. As such, via operation of thesecond blower 432 and the additional filter 470, the air handling unit402 may be configured to provide a portion of the total volume of air toachieve the desired air changes for the room 442 (e.g., two airchanges), instead of providing enough air to achieve the total number ofair changes for the room 442 (e.g., four air changes). Accordingly, anoverall size of the air handling unit 402 may be reduced, as compared toa system having an air handling unit configured to provide four airchanges to the room 442, for example.

In some embodiments, the controller 500 may receive data or feedbackindicative of a temperature (e.g., a current temperature) of the room442 from the sixth sensor 492 (e.g., a thermostat). In response to adetermination that the temperature in the room 442 exceeds a targettemperature set point (e.g., a user-selected target temperature), thecontroller 500 may operate the second heat exchanger 434 to condition(e.g., reduce a temperature of) the return air 440 drawn into theterminal unit 404 (e.g., via the second blower 432).

For example, the controller 500 may operate the chiller system 446 oranother suitable heat exchange system to provide conditioned fluid(e.g., the working fluid 496) to second heat exchanger 434 via thesupply line 448. The controller 500 may control components of the HVACsystem 400 to regulate a flow rate and/or a temperature of the chilledworking fluid 496 supplied to the second heat exchanger 434 (e.g., viathe supply line 448). In this way, the controller 500 may adjust atemperature of the conditioned return air 444 output by the second heatexchanger 434 and, thus, adjust (e.g., increase or decrease) thetemperature of the supply air 450 directed into the room 442 (e.g., viathe DV diffuser 454). The controller 500 may operate the second heatexchanger 434 in this manner to achieve a current temperature within theroom 442 that is substantially equal to (e.g., within a threshold rangeof, within a threshold percentage of) the target temperature set pointof the room 442. Additionally or alternatively, the controller 500 mayadjust operation of the air handling unit 402 based on the feedback fromthe sixth sensor 492 to increase or decrease a temperature of theventilation air 408 entering the terminal unit 404.

In any case, the controller 500 may operate the chiller system 446 suchthat a temperature of the second heat exchanger 434 (e.g., a surfacetemperature of the second heat exchanger 434) and/or a temperature ofthe supply line 448 (e.g., surface temperature of the supply line 448)remains above a dew point temperature of the return air 440 and/or abovea dew point temperature of the existing air within the room 442. In thisway, the controller 500 may ensure that the second heat exchanger 434does not condense moisture that may be suspended within the return air440 drawn thereacross, which may result in accumulation of condensate onand/or near the second heat exchanger 434. Further, to this end, thecontroller 500 may ensure that contact between the existing air withinthe room 442 and the supply line 448 does not result in the formation ofcondensate on the supply line 448. In other words, the controller 500may enable dry cooling (e.g., sensible cooling) of the return air 440,which may reduce or substantially inhibit accumulation of impuritiesand/or organic matter on the second heat exchanger 434 and/or the supplyline 448. As such, the controller 500 may increase a time intervalbetween maintenance cycles of the HVAC system 400 (e.g., cleaning of oneor more coils of the second heat exchanger 434) and may enhance sanitaryoperation of the HVAC system 400. Further, by providing sensible coolingvia the second heat exchanger 434, condensate collection equipment suchas drain pans, pipes, and/or pumps may be omitted from the terminal unit404.

In some embodiments, the controller 500 may be configured to adjustoperation of the chiller system 446 to ensure that a temperature of thechilled working fluid 496 output by the chiller system 446 remains abovethe dew point temperature of the return air 440 and/or above the dewpoint temperature of the existing air within the room 442. For example,in some embodiments, the controller 500 may be configured to receivedata or feedback from the third sensor 486 indicative of a temperatureand/or a humidity level of the return air 440. The controller 500 mayutilize the feedback to calculate the dew point temperature of thereturn air 440 and may instruct the chiller system 446 to output chilledworking fluid 496 at a temperature above the dew point temperature ofthe return air 440. That is, the controller 500 may instruct the chillersystem 446 to output chilled working fluid 496 at a temperature that isabove the dew point temperature of the return air 440 by a thresholdvalue and/or by a threshold percentage, for example. In certainembodiments, the controller 500 may adjust a flow rate of the chilledworking fluid 496 output by the chiller system 446 such that atemperature of the chilled working fluid 496 arriving at the second heatexchanger 434 is above the dew point temperature of the return air 440.

In some embodiments, a temperature of the ventilation air 408 receivedfrom the air handling unit 402 may be substantially equal to or lessthan the target temperature setpoint for the room 442. In suchembodiments, the ventilation air 408 output by the air handling unit 402may be sufficient to satisfy the cooling demand of the room 442, suchthat the controller 500 may stay (e.g., temporality block) operation ofthe chiller system 446. That is, the controller 500 may operate thesecond blower 432 to draw the return air 440 across the second heatexchanger 434, while the second heat exchanger 434 is in an inactivestate, to mix the return air 440 with the ventilation air 408 enteringthe terminal unit 404.

In some embodiments, the terminal unit 404 may include one or moredampers 550 (e.g., control mechanisms, flow control devices, variableair volume [VAV] devices) that may enable the return air 440 to bypassthe second heat exchanger 434 (e.g., during operational periods in whichthe second heat exchanger 434 is inactive) and enter the interior of theterminal unit 404. For example, the controller 500 may be configured toinstruct the dampers 550 to transition to an open configuration whilethe second heat exchanger 434 is inactive (e.g., not circulating chilledworking fluid 496), such that the second blower 432 may draw the returnair 440 into the terminal unit 404 and mix the return air 440 with theventilation air 408 without directing the return air 440 across thesecond heat exchanger 434. Conversely, during operational periods inwhich the second heat exchanger 434 is active (e.g., circulating thechilled working fluid 496), the controller 500 may instruct the dampers550 to close such that the second blower 432 may draw the return air 440across the second heat exchanger 434. In some embodiments, the one ormore dampers 550 may be configured to control a flow rate of theventilation air 408 from the first ductwork 406 into the terminal unit404 and/or control a flow rate of the supply air 450 discharged from theterminal unit 404 into the second ductwork 456.

The DV diffuser 454 may include the outlet 458 configured to dischargethe supply air 450 along the floor 520 of the room 442. Across-sectional area of the outlet 458 may be relatively large, suchthat a discharge velocity of the supply air 450 from the DV diffuser 454is relatively low. In this manner, the DV diffuser 454 may disperse thesupply air 450 (e.g., cooled air) along the floor 520 withoutsubstantially generating turbulent airflow throughout other portions ofthe room 442. That is, the DV diffuser 454 may facilitate supply offresh supply air 450 (e.g., filtered air, conditioned outdoor air 422)to the room 442 while avoiding turbulent interaction between the supplyair 450 and stale or existing air in the room 442. As the supply air 450in the room 442 is gradually heated (e.g., via interaction with thefloor 520, with human occupants within the room 442, with other heatsources), the supply air 450 may rise from the floor 520 toward aceiling 552 of the room 442. The exhaust duct 510 may be positioned nearthe ceiling 552 and be configured to discharge the heated supply air 450from the room as exhaust air 512.

In some embodiments, the third enclosure 452 (e.g., housing) of the DVdiffuser 454 may define a plenum of the DV diffuser 454, which may befluidly coupled to the second ductwork 456. A grille 556 may beremovably coupled to the third enclosure 452 and be configured toposition or retain the filter 459 across the outlet 458 of the DVdiffuser 454. That is, the grille 556 may be configured to removablycouple the filter 459 to the third enclosure 452. In some embodiments,the grille 556 may be removeable by an occupant within the room 442 toprovide the occupant with access to the filter 459. Accordingly, theoccupant may remove the filter 459 for cleaning and/or replacement witha new filter. In certain embodiments, the filter 459 may be sealed orotherwise secured to the third enclosure 452 via a continuous frame(e.g., knife edge frame) that may be formed on the third enclosure 452.Further, a seal (e.g., a gelatinous solution) may be placed between thethird enclosure 452 and the filter 459 to mitigate or substantiallyblock air flow between the third enclosure 452 and the filter 459.

In some embodiments, the third enclosure 452 may include a first panel560 or wall, a second panel 562 or wall, an upper panel 564 or wall, anda lower panel or wall that, together with the grille 556, may bound aninterior region of the third enclosure 452. The first panel 560 and thesecond panel 562 may converge at a vertex 568 that may be configured toalign with a corner 570 of the room 442 (e.g., an intersection of wallsof the room 442). As such, the DV diffuser 454 may be positioned withinthe corner 570 in a space efficient manner and be configured to outputsupply air 450 to the room 442 outwardly from the corner 570 and towarda central region of the room 442. The grille 556 may be configured toextend across the outlet 458 from the first panel 560 to the secondpanel 562. As such, the grille 556, the first panel 560, and the secondpanel 562 may bound an interior region (e.g., a plenum) of the thirdenclosure 452.

FIG. 6 is a cross-sectional side view of an embodiment of the DVdiffuser 454. In the illustrated embodiment, the DV diffuser 454includes the third enclosure 452, the grille 556, and the filter 459positioned between the third enclosure 452 and the grille 556. Asdiscussed above, the third enclosure 452 and the grille 556 maycollectively bound an interior region or plenum 571 of the DV diffuser454. The plenum 571 may be fluidly coupled to an inlet 572 of the thirdenclosure 452, which may be configured to couple to the first ductwork406 and receive the supply air 450.

In some embodiments, the grille 556 (e.g., a cover face) may bedetachable (e.g., fully removeable) from the third enclosure 452 toenable user access to the filter 459 extending across the outlet 458 ofthe DV diffuser 454. In certain embodiments, the grille 556 may bepivotably and/or angularly displaceable relative to the third enclosure452 to enable user access to the filter 459. In some embodiments, thegrille 556 may be configured to house (e.g., couple to) the filter 459and/or may include a diffuser face that is perforated.

As set forth above, embodiments of the present disclosure may provideone or more technical effects useful for facilitating conditioning ofspaces serviced by an HVAC system while mitigating or substantiallyeliminating mixing (e.g., turbulent mixing) of air supplied to the spacewith existing air in each of the spaces, and while mitigating orsubstantially eliminating exchange of air between the different spaces.As such, the improved HVAC system disclosed herein may mitigate orsubstantially eliminate exchange of air between individual rooms, zones,or other spaces serviced by the HVAC system to substantially inhibittransmission of airborne contaminants between the individual spaces,while still providing conditioning to each of the spaces.

It should be understood that the technical effects and technicalproblems in the specification are examples and are not limiting. Indeed,it should be noted that the embodiments described in the specificationmay have other technical effects and can solve other technical problems.

While only certain features and embodiments of the present disclosurehave been illustrated and described, many modifications and changes mayoccur to those skilled in the art, such as variations in sizes,dimensions, structures, shapes and proportions of the various elements,values of parameters, such as temperatures and pressures, mountingarrangements, use of materials, colors, orientations, and so forth,without materially departing from the novel teachings and advantages ofthe subject matter recited in the claims. The order or sequence of anyprocess or method steps may be varied or re-sequenced according toalternative embodiments. It is, therefore, to be understood that theappended claims are intended to cover all such modifications and changesas fall within the true spirit of the present disclosure. Furthermore,in an effort to provide a concise description of the exemplaryembodiments, all features of an actual implementation may not have beendescribed, such as those unrelated to the presently contemplated bestmode of carrying out the present disclosure, or those unrelated toenabling the claimed embodiments. It should be appreciated that in thedevelopment of any such actual implementation, as in any engineering ordesign project, numerous implementation specific decisions may be made.Such a development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure, without undue experimentation.

The techniques presented and claimed herein are referenced and appliedto material objects and concrete examples of a practical nature thatdemonstrably improve the present technical field and, as such, are notabstract, intangible or purely theoretical. Further, if any claimsappended to the end of this specification contain one or more elementsdesignated as “means for [perform]ing [a function] . . . ” or “step for[perform]ing [a function] . . . ”, it is intended that such elements areto be interpreted under 35 U.S.C. 112(f). However, for any claimscontaining elements designated in any other manner, it is intended thatsuch elements are not to be interpreted under 35 U.S.C. 112(f).

1. A heating, ventilation, and/or air conditioning (HVAC) system,comprising: an air handling unit configured to condition an outdoor airflow to generate a ventilation air flow; a terminal unit fluidly coupledto the air handling unit and comprising: a plenum configured to receivethe ventilation air flow; and a blower configured to draw a return airflow from a space serviced by the HVAC system across a heat exchanger ofthe terminal unit and into the plenum to condition the return air flow,wherein the blower is configured to mix the ventilation air flow and thereturn air flow to generate a supply air flow; and a displacementventilation (DV) diffuser fluidly coupled to the terminal unit andconfigured to receive the supply air flow, wherein the DV diffuser isconfigured to receive a filter configured to filter the supply air flow,and wherein the DV diffuser is configured to direct the supply air flowthrough the filter and into the space.
 2. The HVAC system of claim 1,comprising the filter, wherein the filter comprises a high efficiencyparticulate air (HEPA) filter configured to capture particles having asize between 1.0 micron and 3.0 microns in diameter.
 3. The HVAC systemof claim 1, wherein the heat exchanger is configured to circulate aworking fluid at a temperature above a first dew point temperature ofthe return air flow to cool the return air flow without dehumidifyingthe return air flow.
 4. The HVAC system of claim 3, wherein the airhandling unit comprises an additional heat exchanger configured tooperate below a second dew point temperature of the outdoor air flow tocool and dehumidify the outdoor air flow.
 5. The HVAC system of claim 3,comprising: one or more sensors configured to acquire feedbackindicative of a temperature of the return air flow, a humidity of thereturn air flow, or both; and a controller communicatively coupled tothe one or more sensors and configured to receive the feedback, whereinthe controller is configured to determine the first dew pointtemperature based on the temperature of the return air flow, thehumidity of the return air flow, or both.
 6. The HVAC system of claim 5,comprising a chiller system configured to provide the working fluid tothe heat exchanger, wherein the controller is configured to control thechiller system to maintain the temperature of the working fluid abovethe first dew point temperature.
 7. The HVAC system of claim 1, whereinthe terminal unit comprises an additional filter, and wherein the bloweris configured to draw the return air flow across the additional filter.8. The HVAC system of claim 7, wherein the additional filter comprises aHEPA filter, a MERV-6 filter, or a MERV-8 filter.
 9. The HVAC system ofclaim 1, wherein the terminal unit comprises a reheat coil configured toreceive the supply air flow and heat the supply air flow.
 10. The HVACsystem of claim 1, comprising: a ventilation duct fluidly coupling theair handling unit and the terminal unit; an exhaust duct fluidly coupledto the space and to an outdoor environment; and an exhaust blowerconfigured to draw an exhaust air flow from the space and discharge theexhaust air flow to the outdoor environment via the exhaust duct,wherein the air handling unit, the ventilation duct, and the terminalunit do not receive a portion of the exhaust air flow from the exhaustduct.
 11. The HVAC system of claim 1, wherein the terminal unit isconfigured to be positioned adjacent to a ceiling of the space and theDV diffuser is configured to be positioned adjacent to a floor of thespace.
 12. A displacement ventilation (DV) diffuser, comprising: anenclosure comprising an inlet configured to receive an air flow and anoutlet configured to discharge the air flow, wherein the enclosure isconfigured to receive a high efficiency particulate air (HEPA) filtersuch that the HEPA filter extends across the outlet and is configured tofilter the air flow; and a grille removeably coupled to the enclosureand configured to secure the HEPA filter to the enclosure.
 13. The DVdiffuser of claim 12, comprising the HEPA filter, wherein the HEPAfilter is configured to capture particles in the air flow having a sizebetween 1.0 micron and 3.0 microns in diameter.
 14. The DV diffuser ofclaim 12, wherein the enclosure comprises a first wall and a secondwall, wherein the first wall and the second wall converge at a vertex ofthe enclosure, and wherein the grille is configured to extend from thefirst wall to the second wall.
 15. A heating, ventilation, and/or airconditioning (HVAC) system, comprising: an air handling unit comprisinga first heat exchanger configured to dehumidify an outdoor air flow togenerate a ventilation air flow; a terminal unit configured to receivethe ventilation air flow and comprising: a second heat exchangerconfigured to circulate a working fluid; and a blower configured to drawa return air flow across the second heat exchanger to condition thereturn air flow and to mix the return air flow with the ventilation airflow to generate a supply air flow; and a displacement ventilation (DV)diffuser configured to receive the supply air flow and comprising afilter configured to filter the supply air flow, wherein the filtercomprises a high efficiency particulate air (HEPA) filter.
 16. The HVACsystem of claim 15, comprising: a chiller system configured to supplythe working fluid to the second heat exchanger; and a controllerconfigured to determine a dew point temperature of the return air flowbased on feedback from a sensor exposed to the return air flow, whereinthe controller is configured to adjust the chiller system to maintain atemperature of the working fluid above the dew point temperature of thereturn air flow.
 17. The HVAC system of claim 15, wherein the terminalunit is disposed within a space serviced by the HVAC system, and the DVdiffuser is configured to discharge the supply air flow along a floor ofthe space serviced by the HVAC system.
 18. The HVAC system of claim 15,comprising: an exhaust duct fluidly coupled to an outdoor environmentand to a space serviced by the DV diffuser; and an exhaust blowerconfigured to draw an exhaust air flow from the space and discharge theexhaust air flow to the outdoor environment via the exhaust duct,wherein the air handling unit and the terminal unit do not receive aportion of the exhaust air flow from the exhaust duct.
 19. The HVACsystem of claim 15, wherein the terminal unit comprises an additionalfilter, wherein the blower is configured to draw the return air flowacross the additional filter and the second heat exchanger.
 20. The HVACsystem of claim 19, wherein the terminal unit is configured to provideaccess to the additional filter from a space serviced by the DVdiffuser, such that the additional filter is replaceable by an occupantlocated within the space.